I don't know what's changed since the last post(s) on this thread, but I have read SEVERAL workarounds (mostly from Reddit, and even ChatGPT), and NONE of them worked consistently. Even the 'solution' mentioned in this post (using an emoji) doesn't work, as that gets collapsed just like any other "body" text line does.
It seems that the ONLY way to place a hard space in between two collapsed section headers (or subheaders) is to place ANOTHER header (or subheader) line in between them and somehow make that INVISIBLE. But leaving it just BLANK, doesn't work (I tried this, and it SEEMED to work…and then it didn't!) So, at least ONE character or emoji must be placed there to make the header row REAL—the issue is finding a way to make it invisible on BOTH white and black backgrounds (haven't tested this yet). No fumbling for an appropriate emoji—any easily keyboard-accessible character (i.e., "-") would suffice.
OR… I could be totally wrong! LOL